Author Topic: Square holes on aluminum.... how do you do it?  (Read 19871 times)

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Offline tkamiyaTopic starter

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Square holes on aluminum.... how do you do it?
« on: October 09, 2019, 02:24:01 am »
I am placing one of my project in an aluminum rack case.  Front panel is 2mm, top and bottom is about 1.5mm, and sides are 3mm. 

I do not own any mechanized tools.  All hand tools, bench drill press, and manual tools.  I just broke my dremel. 

I always disliked making non-round holes.  But for RS232C (9 pin) and power connectors, square holes are necessary.  My usual method is draw out the outline, drill holes inside it along the line, use whatever is available to connect the holes, then file, file, file....  It's time consuming, and prone to slips to cause cosmetic problems.  I can do pretty precise crafting but boy - it takes time.....

Does anyone know a better way?  What I've already excluded are farming it out to pros, buying mills, and hydraulic punches. 
 

Offline sokoloff

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Re: Square holes on aluminum.... how do you do it?
« Reply #1 on: October 09, 2019, 02:27:22 am »
I use a square nibbler I bought at radio shack many years ago. I’ll see if I can find a modern listing.
 

Offline sokoloff

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Offline digsys

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Re: Square holes on aluminum.... how do you do it?
« Reply #3 on: October 09, 2019, 02:55:09 am »
I used to have a punch set for all sorts of connectors - used both hand press and hydraulic press types. If you're only doing a few, likely not worth while, but damn awesome for production. Also had a set of basic punch tool shapes that you just placed the sheet down and whacked out desired shapes. Worked fine
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Offline texaspyro

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Re: Square holes on aluminum.... how do you do it?
« Reply #4 on: October 09, 2019, 02:55:43 am »
You can buy chassis punches for most DBxx connectors.   They are a 2-piece punch.  You drill a hole,  feed the bolt through the hole, place the second piece over the boltm and crank down a nut.   The punches (made by Greenlee, etc) can be rather expensive, but occasionally can be found on Ebay for affordable prices.
 

Offline tkamiyaTopic starter

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Re: Square holes on aluminum.... how do you do it?
« Reply #5 on: October 09, 2019, 03:09:48 am »
This is the WINNER!  Thanks!  Some of these and nibbler should take care of my needs.  Although....  nibblers I had in the past could not handle more than 1mm thick aluminum.  Cutting blade would bend and eventually break off.

I think I just need DB9 and AC socket type to get started. 

ps.  Wow...  db25 kind is going for $500 new at Amazon! and this is just for the punch itself!
 

Offline Bud

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Re: Square holes on aluminum.... how do you do it?
« Reply #6 on: October 09, 2019, 03:15:09 am »
All of a sudden farming it to pros does not look that bad anymore ?  >:D
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Offline tkamiyaTopic starter

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Re: Square holes on aluminum.... how do you do it?
« Reply #7 on: October 09, 2019, 03:43:04 am »
Well.....  all the sudden, drills, files, and a couple of band-aids doesn't seem so bad....

Farming it out is OUT because of the way I make things.  I do in steps.  It's just too inconvenient to make several trips to the shop.  For my current project, I ran into few problems.  Now, I have to remove the front panel, add two DB9 holes and 1 hole for LED.

As far as Greenly punches go, I was reading up some.  For aluminum, the spec for the punch is 3.2mm.  That's awfully close to some of the rack panels.  I really don't want to buy mills as I was never trained to properly use it. 
 

Offline drussell

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Re: Square holes on aluminum.... how do you do it?
« Reply #8 on: October 09, 2019, 03:47:52 am »
ps.  Wow...  db25 kind is going for $500 new at Amazon! and this is just for the punch itself!

Yeah, the "real" ones meant for daily production use are rather pricey.

There must still be a source somewhere for chinesium-grade punch sets that are suitable for occasional use or hobby type applications.  I recall seeing a set of all five D-sub sizes and the drawbar tool for about $150 in the back of some electronics magazine or maybe in Computer Shopper or something, many many years ago.  Seemed like a great deal, even if they weren't very robust. 

I almost bought a set since in those days I used to fairly regularly have to cut extra port holes into the back of computers being built, upgraded or modified back then, but I never did get a set.  Most of the chassis we were dealing with started coming with ample cutouts, even some with knockouts for the big SCSI connectors, although I wished I had a set many times later when building some other random projects, etc. as well.  :)

They aren't that difficult to make (random dies and punches) strong enough for aluminum, plastic or very thin steel, I've made a few purpose-built ones over the years for various things, but if someone can find a source of some pre-made ones in some common modern styles, etc. it would be convenient.

I usually end up doing most of my panels on my old 1980s Dahlgren Wizzard XL computerized engraver.  It's a bit of a pain to set up to cut panels and such compared to today's modern generic CNC router systems, but what do you expect for a 30+ years old system with TRS-80 internals for brains that was intended for doing things like making signs.  :)

I'm just glad the thing still works!
« Last Edit: October 09, 2019, 03:51:54 am by drussell »
 

Offline PixieDust

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Re: Square holes on aluminum.... how do you do it?
« Reply #9 on: October 09, 2019, 04:20:58 am »
Use square drill bits.

But yer, files are the way to go.
 

Offline rpetitho

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Re: Square holes on aluminum.... how do you do it?
« Reply #10 on: October 09, 2019, 04:21:45 am »
I used a combination of drills and jigsaws on my isolation transformer enclosure. Worked pretty good for bigger holes. Smaller holes are a different challenge.

-Bob
 

Offline viperidae

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Re: Square holes on aluminum.... how do you do it?
« Reply #11 on: October 09, 2019, 05:40:49 am »
Square drill bits are just for wood aren't they?
 

Offline beanflying

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Re: Square holes on aluminum.... how do you do it?
« Reply #12 on: October 09, 2019, 06:00:33 am »
Nibblers for the win on thin sheetmetal and even plastics but you are limited to about 2mm max. The best bit is if you are working in enclosures with other electrical stuff still inside then the chips are way less floaty and easier to cleanup than every other method. Minimal buckling as well on even thin materials over using tin snips or shears.

I would seriously love the money to spare for a set of hydraulic punches but it would be a total indulgence and so drills files and a Dremel for the other jobs.

Tips - Masking tape for the tool side (not the die side) to minimize scratching and buy a deburring tool (the blue handled thing) and use your Laser Cutter to do the mark out for accuracy ;)
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Offline EEEnthusiast

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Re: Square holes on aluminum.... how do you do it?
« Reply #13 on: October 09, 2019, 06:05:58 am »
Buy a cheap CNC router machine from China. Something like this

https://www.aliexpress.com/item/32919397764.html?spm=a2g0o.productlist.0.0.54db57f5O012h9&algo_pvid=c1d5f8e0-b557-4959-bcf6-b11b82acb20c&algo_expid=c1d5f8e0-b557-4959-bcf6-b11b82acb20c-7&btsid=e9376042-133e-4e2f-8bca-df0b401da4fa&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_53

It can cut any shape on metal sheets and it is really precise for hobbyist. I have the same one and have cut square holes on 1.6mm thick Aluminium sheets.
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Offline GeorgeOfTheJungle

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Re: Square holes on aluminum.... how do you do it?
« Reply #14 on: October 09, 2019, 06:39:10 am »
Three great tools:

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Offline mikerj

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Re: Square holes on aluminum.... how do you do it?
« Reply #15 on: October 09, 2019, 11:26:46 am »
Square drill bits are just for wood aren't they?

You can broach square (or other shaped) holes in metal, and you can use a rotary broach for symmetrical shapes, but it's not a drill bit.
 

Offline dom0

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Re: Square holes on aluminum.... how do you do it?
« Reply #16 on: October 09, 2019, 02:27:17 pm »
Good files make very quick work of aluminium. Make sure you are actually using an aluminium alloy that can be machined; AlMg1 for example is very hard to machine due to its softness, but commonly sold on eBay etc. because it's cheap. AlMg3 is better and proper machining alloys are very easy to work - you can drill them easily, get excellent chips, very little burrs etc.

You will also immediately notice that a front panel from a higher grade alloy is much more rigid and doesn't bend nearly as easy as a panel made from a low-strength alloy like AlMg1.

Chalking files reduces edge build up drastically and prevents chips getting stuck in the files. Make sure your drill bits don't have built up edges. For D-Sub connectors you want a round file to work the corners, diameter of around ~5 mm.
« Last Edit: October 09, 2019, 02:30:11 pm by dom0 »
,
 
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Online SiliconWizard

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Re: Square holes on aluminum.... how do you do it?
« Reply #17 on: October 09, 2019, 03:07:55 pm »
Punch, punch, punch... (and Judy? ::) )
 

Online Conrad Hoffman

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Re: Square holes on aluminum.... how do you do it?
« Reply #18 on: October 09, 2019, 04:29:08 pm »
We have a shop near here that does a great job on electrical panels using a waterjet cutter. Not very expensive either.
 

Online langwadt

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Re: Square holes on aluminum.... how do you do it?
« Reply #19 on: October 09, 2019, 04:37:55 pm »
jewelers saw?
 

Offline duak

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Re: Square holes on aluminum.... how do you do it?
« Reply #20 on: October 09, 2019, 05:45:00 pm »
Been there, done that.  I spent hours filing square & D shaped holes in both alum, steel & stainless steel.

Some tools that helped me are:
 - nibbler,
 - good files and a file card to clean them. If you don't have handles for the smaller ones use wire nuts from electrical wiring - just screw them on & save your fingers,
 - stepped drill bit (Unibit et al) for sheet metal - these bits don't grab sheet metal like twist drills do - get one!
 - tapered reamer to enlarge holes,
 - wide heavy black ink marker & sharp scriber to mark outlines and center lines,
 - sharp center punch - automatic center punch even better,
 - edge & hole deburring tools,
 - vise and rubber faced jaws,
 
 

Offline L_Euler

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Re: Square holes on aluminum.... how do you do it?
« Reply #21 on: October 09, 2019, 10:58:35 pm »
Get a scroll saw off eBay and a handful of round abrasive blades.  You can then dress the corners with needle files.
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Offline KL27x

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Re: Square holes on aluminum.... how do you do it?
« Reply #22 on: October 09, 2019, 11:43:15 pm »
Quote
buying mills
You don't need a mill to cut aluminum. Dremel tool and a 1/8" coarse carbide burr will get you close (looks like an endmill but with diamond shaped points on it instead of continuous cutting edge like a twist drill). This will leave less work to be done with the file.

A router table or drill press will allow better control, but you can do it freehand. Concentricity/runout matters, so just don't buy generic rotary tools. Dremel or Proxxon are the only things to bother with, IMO. A cheap one will do it, if you find the right pressure and rpm to avoid loosening your fillings, but the cutting efficiency will be very low, cuz it will only cut on one part of the bit.
« Last Edit: October 09, 2019, 11:45:42 pm by KL27x »
 

Offline thermistor-guy

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Re: Square holes on aluminum.... how do you do it?
« Reply #23 on: October 10, 2019, 01:50:15 am »
...I always disliked making non-round holes.  But for RS232C (9 pin) and power connectors, square holes are necessary.  My usual method is draw out the outline, drill holes inside it along the line, use whatever is available to connect the holes, then file, file, file....
Does anyone know a better way?  ...

I make D-subminiature connector cut-outs on DIY test jigs. My tools are similar to yours: Dremel and accessories, files, Roper Whitney hand punch.

My method for preventing cosmetic damage is to print the cut-outs, and other details, on adhesive A4 labels, 1:1, and stick the labels over the blank panels. Add masking tape over metal edges.

You can include other details on the label, like critical dimensions, connector designation, pin 1 location, panel type and version number, design file name, and so on - very handy to have all the info you need right in front of you as you work.
 

Offline beanflying

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Re: Square holes on aluminum.... how do you do it?
« Reply #24 on: October 10, 2019, 02:25:21 am »
Sticky labels work really well in particular if it is a job you are likely to repeat. Due to the raised lip the nibbler wouldn't reach some of it so it was a combo nibble, saw and file. Catching the leavings as it was still attached to an otherwise working bit of HP'ness needed a little bodge. No smoke has escaped since so I think I caught all the bits.

Coffee, Food, R/C and electronics nerd in no particular order. Also CNC wannabe, 3D printer and Laser Cutter Junkie and just don't mention my TEA addiction....
 


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